CDN Migration Guide: Switch CDNs With Zero Downtime
Switching CDNs sounds scary — but with the right steps, you can migrate in under 30 minutes with no downtime and no SEO impact.
Pre-Migration Checklist
- Document current DNS settings (take screenshots)
- Note all custom SSL certificates
- List all cache rules and page rules
- Backup your origin server configuration
- Choose a low-traffic time window
Step-by-Step Migration
Step 1: Set Up New CDN
Create a Pull Zone on BunnyCDN pointing to your origin server. Test with the temporary .b-cdn.net domain.
Step 2: Configure SSL
Provision Let's Encrypt certificate on the new CDN. Verify HTTPS works on the temp domain.
Step 3: Replicate Cache Rules
Copy your cache TTLs, bypass rules, and compression settings from old CDN to new.
Step 4: DNS Cutover
Update CNAME record to point to new CDN. Keep TTL low (60 seconds) during transition. Both CDNs will serve traffic during propagation.
Step 5: Monitor & Verify
Check SSL, cache hit ratio, origin load. Monitor for 24 hours before decommissioning old CDN.
Common Migration Mistakes
- Forgetting to update CSP headers with new CDN domain
- Not testing checkout/payment flows after migration
- Setting DNS TTL too high before cutover (use 60s, not 3600s)
- Deleting old CDN too quickly — keep it as backup for 48 hours